A long term evolution (LTE) radio access technology (RAT) may be deployed on an unlicensed frequency spectrum, which is also known as LTE-Unlicensed (LTE-U). One of possible deployment scenarios for the LTE-U is to deploy an LTE-U carrier as a part of carrier aggregations, where an LTE-U carrier is aggregated with another carrier on a licensed spectrum. In a conventional arrangement, a carrier on a licensed spectrum is assigned as a primary cell (PCell) and a carrier on an unlicensed spectrum is assigned as a secondary cell (SCell) for a UE. Since there may be other RATs operating on the same unlicensed spectrum as the LTE-U carrier, there is a need to enable co-existence of other RAT with LTE-U on an unlicensed frequency spectrum without undesirable interference between heterogeneous RATs.